Relocated & split up darwin & nixos modules

I broke out host specific bits from the configuration that should be
common to all hosts of a given type.

modules/common/nixos/all-hosts.nix

@@ -0,0 +1,49 @@
+{ config, pkgs, ... }: {
+  imports = [
+    ./internationalisation.nix
+  ];
+
+  environment = {
+    shells = with pkgs; [ bash zsh ];
+    systemPackages = with pkgs; [
+      angryipscanner
+      dconf2nix
+      file
+      neofetch
+      python3
+      tailscale
+    ];
+  };
+
+  fonts.fontDir.enable = false;
+  fonts.packages = with pkgs; [
+    font-awesome
+    (nerdfonts.override {
+      fonts = [
+        "Hack"
+        "SourceCodePro"
+      ];
+    })
+  ];
+
+  nix.settings = {
+    experimental-features = [
+      "flakes"
+      "nix-command"
+    ];
+  };
+
+  programs = {
+    zsh.enable = true;
+  };
+
+  security.sudo.wheelNeedsPassword = false;
+
+  services.tailscale = {
+    enable = true;
+  };
+
+  time.timeZone = "America/New_York";
+
+  users.defaultUserShell = pkgs.zsh;
+}

modules/common/nixos/internationalisation.nix

@@ -0,0 +1,17 @@
+{ config, pkgs, ... }: {
+  # Select internationalisation properties.
+  i18n = {
+    defaultLocale = "en_US.UTF-8";
+    extraLocaleSettings = {
+      LC_ADDRESS = "en_US.UTF-8";
+      LC_IDENTIFICATION = "en_US.UTF-8";
+      LC_MEASUREMENT = "en_US.UTF-8";
+      LC_MONETARY = "en_US.UTF-8";
+      LC_NAME = "en_US.UTF-8";
+      LC_NUMERIC = "en_US.UTF-8";
+      LC_PAPER = "en_US.UTF-8";
+      LC_TELEPHONE = "en_US.UTF-8";
+      LC_TIME = "en_US.UTF-8";
+    };
+  };
+}